The Histogenesis of Cysticercus pisiformis. 191 



In m}^ own preparations, owing- to the presence of acid in all 

 my fixatives, I have not obtained the chalk bodies in normal con- 

 dition at any stage. The places formerly occupied by them appear 

 as oval spaces varying- from those which are greatly flattened to 

 those which are round or nearly so and usually — perhaps always, 

 but this cannot be determined with certainty — containing- a 

 remnant of the concretion. ^) These spaces vary considerably in size 

 and form due partly to the stage of development of the concretion 

 and partly to the state of contraction of the worm when killed. 

 They appear during the early development of the head piece and 

 soon become very numerous in the neck region of the larva, while 

 in the bladder wall they are scarce or wanting. 



In places where the tissue is compact and the concretions 

 numerous, it is difficult to find any relation between the latter and 

 the nuclei of the parenchjmia ; the existence of a definite nucleus to 

 each concretion is impossible to determine. But where the paren- 

 chyma is loose and the concretions few, it is frequently possible to 

 find a nucleus in relation with each concretion cavity. As is clearly 

 shown by Blochmann (1896, fig. 5, tab. 2), the cell body is in no 

 way in connection with the concretion remnant, but surrounds the 

 latter like a sac. My own observations, however, have shown that, 

 as is suggested by Blochmaxk's fig. 2, tab. 2, the ceU of the chalk 

 body is nothing more nor less than an ordinary parenchyma 

 cell belonging to the parenchyma network immediately 

 surrounding the space occupied by the concretion. 

 This is confirmed by some sections of Taenia sei-rafa, in whicli the 

 concretions were comparatively little injured by the fixative, where 

 the same relation has been found (see Fig. 3). I therefore incline 

 strongly to the view of Leuckaet (1879—86), that the chalk body 

 is formed as an intercellular deposit, h avingno direct 

 connection with any cell. As further evidence in support of 

 this view, the reader is referred to Fig. 2 in which is shown a 

 chalk body with two parenchyma cells in close apposition therewith. 

 Now, if the concretion has been deposited within one of these, 

 what is there to show to which one it belongs? 



1) The precise nature of this remnant is not known, Gkiesbach 

 (1883) assumed it to be of an organic nature, perhaps a double salt of 

 calcium carbonate and albuminate. 



